Expandable Functional TFE Copolymer Fine Powder, Expanded Products and Reacted Products Therefrom

ABSTRACT

A functional TFE copolymer fine powder is described, wherein the TFE copolymer is a polymer of TFE and at least one functional comonomer, and wherein the TFE copolymer has functional groups that are pendant to the polymer chain. The functional TFE copolymer fine powder resin is paste extrudable and expandable. Methods for making the functional TFE copolymer are also described. The expanded functional TFE copolymer material may be post-reacted after expansion.

RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 12/886,817 filed Sep. 21, 2010 which is acontinuation-in-part application of pending U.S. patent application Ser.No. 12/410,050 filed Mar. 24, 2009.

FIELD OF THE INVENTION

Expandable TFE copolymer fine powder resins containing functionalmonomers, expanded functional products obtained from these copolymers,and processes for making them are described herein. Further describedare post-expansion reactions of the expanded functional TFE copolymermaterials, and products made therefrom.

BACKGROUND OF THE INVENTION

Polytetrafluoroethylene or PTFE is known to have a unique combination ofproperties including excellent chemical resistance, thermal stability athigh temperature, low surface energy and excellent electrical(dielectric) properties. PTFE is also known to have two deficiencieswhich limit its use: high cold flow or creep and poor resistance toionizing radiation.

Stretching certain forms of PTFE to make microporous expanded PTFE(ePTFE) can improve strength, decrease cold flow or creep, and improvethe dielectric properties without changing surface or chemicalproperties. The chemical resistance or inertness, as well as the lowsurface energy, of PTFE and ePTFE are beneficial properties for someapplications. But for other applications, it would be beneficial toselectively modify these properties without degrading the polymer.

There has been significant research to modify the surface or chemicalproperties of PTFE and microporous ePTFE in order to improve adhesionand compatibility with other materials. For example, efforts haveincluded attempts to decrease creep by radiation crosslinking, increaseor decrease the surface free energy (e.g. increase or decreasehydrophilicity), and provide sites for chemical reactions to improve theutility of PTFE and/or ePTFE in specific applications by chemical andplasma treatments.

Recently, plasma treatment of microporous ePTFE in the presence ofmaleic anhydride is reported to have produced acid functionality on thesurface of the microporous ePTFE. Though the exact mechanism of thesesurface reactions is not reported, it likely results from the formationof free radicals by bond scission. Where carbon-carbon bond strength isknown to be about forty percent lower than carbon-fluorine bonds, amajority of the radicals would result from scission of the carbon-carbonbonds, or main polymer chain scission, thereby decreasing the molecularweight of the polymer, and restricting the anhydride or acidfunctionality to the ends of the degraded polymer chains. Plasma graftpolymerization is restricted near the surface of the sample. (PlasmaSurface Modification and Plasma Polymerization; N. Inagoki, TechnomicPublishing, 1996, p. 44).

Techniques for dispersion polymerization of both tetrafluoroethylene(TFE) monomer and TFE copolymers have been described. There arereferences which define and distinguish TFE copolymers based on theconcentration of the comonomer. TFE polymers containing less than 1weight percent comonomer have been referred to as modified homopolymers,or modified PTFE, whereas TFE polymers containing more than 1 weightpercent comonomer have been referred to as TFE copolymers.(Fluoroplastics—Vol 1; Non-Melt Processible Fluoroplastics; WilliamsAndrew, Inc., Norwich, N.Y., at p. 19 (2000).) However, for use herein,TFE polymers containing one or more comonomers at any concentration willbe defined as TFE copolymers.

In some processes, dispersion polymerization of TFE produces a resinthat has come to be known as “fine powder.” (e.g., U.S. Pat. No.4,016,345 (Holmes, 1977)). Generally, in such processes, sufficientdispersing agent is introduced into a water carrier such that, uponaddition of TFE monomer in the presence of a suitable polymerizationinitiator and, upon agitation and under autogenous TFE pressure of 10-40kg/cm², polymerization proceeds until the desired level of colloidallydispersed polymer particles is reached and the reaction is then stopped.The dispersed polymer particles may subsequently be coagulated by knowntechniques to obtain the fine powder form of the polymer. The finepowders are dried at temperatures from about 100 to 200° C.

Fine powder resins are known to be useful in paste extrusion processesand in stretching (expansion) processes in which the paste-extrudedextrudate, after removal of extrusion aid lubricant, is stretched toproduce porous, strong products of various cross-sectional shapes suchas rods, filaments, sheets, tubes, etc. Such a stretching process isdisclosed in commonly owned U.S. Pat. No. 3,953,566 (“'566” to Gore).The expansion process as it applies to fluorocarbon polymers isdescribed in the aforesaid '566 patent. As used herein, articles thatcan be expanded by the process of the '566 patent are said to be“expanded” and the resins used in the expansion process to create sucharticles are said to be expandable TFE polymers or expandable TFEcopolymers.

Dispersion processes to make TFE copolymers are taught in for example,in U.S. Pat. No. 4,792,594 (Gangal et al.), U.S. Pat. No. 6,541,589(Baillie), U.S. Pat. App. 2007/0010642 (Sabol and Baillie) and U.S.patent application Ser. No. 11/906,877 (Ford; filed Oct. 4, 2007).Dispersion processes to make copolymers are also described. It is taughtthat fine powders made by these dispersions may be paste extruded andprocessed by the processes disclosed in U.S. Pat. No. 3,953,566 to makemicroporous expanded products. TFE fine powder polymer processed bypaste extrusion or expansion has high crystallinity especially for theportion of polymer formed in the later stage of the polymerization. Thismaterial is sometimes described as the shell or the sheath of thedispersion particle.

TFE copolymers processable by melt extrusion and injection moldinginclude TFE-HFP (hexafluoropropylene) copolymers known as FEP, TFEperfluoroalkyl vinyl ether copolymers known as PFA and MFA, and TFEethylene copolymers known as E-TFE. These polymers are not fine powdersand cannot be paste extruded or expanded into microporous productsbecause of low crystallinity.

TFE copolymers made from fluorovinyl ether comonomers having sulfonylfluoride groups, ester groups and cyano groups have been describedhaving the formulae:

CF₂═CF—O R_(f) SO₂F   I.

CF₂═CF—O R_(f) COOCH₃   II.

CF₂═CF—O R_(f) CN   III.

where R_(f) is fluoroalkyl or fluoroalkyl ether. (Fluoroplastics-Vol. 2;Melt Processible Fluoropolymers; Williams Andrew Inc.; PerfluorinatedIonomer Membranes, American Chemical Society Symposium, Series 180,1982; U.S. Pat. No. 3,692,569 (Grot); Moore, Albert L. FluoroelastomersHandbook, William Andrew Publishing, 2006). Monomers of structures I andII are copolymerized with TFE to form polymers subsequently hydrolyzedto form the sulfonic acid and carboxylic acid. However, these polymerscontain sufficient concentration of comonomer that there is little ifany crystallinity in the polymers. Monomers of structure III have beenpolymerized with TFE and perfluoroalkylvinyl ethers to make perfluoroelastomers where monomer with structure III is the cross link site forthe elastomers. The materials have little or no crystallinity and aretherefore not expandable to create microporous materials.

U.S. Pat. App. 2006/0270780 (Xu et al.) teaches a PTFE modified with acyanovinyl ether cross linking monomer in a microemulsion process. Inthis patent application, the modified PTFE is not a fine powder andcannot be paste extruded and expanded according to the '566 process.

U.S. Pat. No. 7,019,083 (Grootaert) teaches low molecular weight meltprocessable TFE perfluoropropylvinyl ether (PPVE) copolymer containing acyanovinyl ether that is not formed as a fine powder and which wouldlack sufficient crystallinity to be paste extruded and be processed intomicroporous products. U.S. Pat. No. 4,326,046 (Miyaka) teaches makingmodified PTFE by including 0.001 to 10 mol % of a comonomer componenthaving an acid type functional (or precursor to an acid) group. The acidincludes carboxylic, sulphonic or phosphoric acids. U.S. Pat. No.4,326,046, teaches that the particle of the modifiedpolytetrafluoroethylene comprises a core made of homopolymer oftetrafluoroethylene and the modifier component is included in the sheathlayer. U.S. Pat. No. 4,326,046 does not teach paste extruding orexpanding the modified polymer. Materials having the high modifiercomponent polymerized in the later stages of polymerization would nothave sufficient crystallinity to be processed into microporous productsby the '566 process.

U.S. Pat. No. 7,342,066 to Dadalas et al. teaches use of a PTFEdispersion in a coating process. The PTFE contains up to 1 weightpercent of an ionic comonomer (e.g., a monomer having acid groups suchas an ionic group) where at least a portion and preferably all of thecomonomer is added in the later stage of the polymerization. U.S. Pat.No. 7,342,066 does not teach forming a paste extrudable or expandablefine powder. Materials made with the high comonomer concentration at thelater stages of polymerization would have low crystallinity and wouldnot be paste extrudable or expanded by the processes of the '566 patent.

There is a need for TFE copolymer materials containing functional groupswhich impart specific chemical properties to a polymer, wherein thecopolymer can be expanded to provide a microstructure characterized bynodes interconnected by fibrils. There is a further need for expandedTFE copolymer materials containing functional groups that can undergosubsequent controlled reactions to impart other specific properties tothe expanded material while maintaining properties of the expanded TFEcopolymer material.

SUMMARY OF THE INVENTION

This invention relates to functional TFE copolymers comprising TFE andat least one comonomer that comprises a functional group. The functionalTFE copolymer has functional groups that are pendant to the polymerchain. The pendant functional groups emanate from a branch in thepolymer chain. The functional TFE copolymer can be expanded (stretchedunder controlled conditions) to produce microporous expanded TFEcopolymer material, having a microstructure characterized by nodes (1)interconnected by fibrils (2) (as exemplified in FIGS. 1 and 2).

A process for polymerization of these monomers to produce functional TFEcopolymers is described, as well as dispersions of the functional TFEcopolymer. Moreover, functional TFE copolymer fine powder is describedthat is paste extrudable and expandable into microporous functional TFEcopolymers. The porous functional products produced by expansion of thepolymers, and reactions of the porous functional TFE copolymericmaterials are described.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 SEM photomicrograph of an expanded sheet of functional TFEcopolymer taken at 10,000× magnification.

FIG. 2 SEM photomicrograph of an expanded sheet of functional TFEcopolymer taken at 10,000× magnification.

FIG. 3 is a representation of an immobilization of a bioactive speciesto a functional group;

FIG. 4 is a representation of a group substitution reaction of aninitial functional group, wherein the initial functional group isreacted to form a secondary functional group;

FIG. 5 is a representation of an immobilization of a bioactive speciesto a secondary functional group;

FIG. 6 is a representation of an immobilization of a spacer arm to afunctional group.

DETAILED DESCRIPTION OF THE INVENTION

Described herein are functional TFE copolymers made from an aqueousdispersion polymerization process, and processes for forming finepowders of the functional TFE copolymers that are paste-extrudable andexpandable. The functional TFE copolymer comprises a polymer of TFE andat least one comonomer that contains a functional group. The TFEcopolymers comprise functional groups that are pendant to the polymerchain. A process is provided for making the functional TFE copolymerfine powder from TFE and at least one comonomer containing a functionalgroup. Further described is the microporous expanded TFE copolymerhaving functional groups obtained from the fine powders, and processesfor reacting the microporous expanded TFE copolymer having functionalgroups.

The term TFE copolymer is defined as a TFE polymer comprising one ormore comonomer at any concentration. As used herein the term functionalTFE copolymer is defined as a TFE copolymer having functional groupsthat are pendant to the polymer chain wherein the functional TFEcopolymer is formed by copolymerizing TFE with comonomers having afunctional group. The functional TFE copolymers may be expanded intomicroporous materials. The expanded functional TFE copolymers made bythe processes described herein have a microstructure characterized bynodes interconnected by fibrils and the copolymers have a functionalgroup pendant to the polymer chain.

As used herein, the term functional comonomer is a monomer thatcopolymerizes with TFE in a dispersion polymerization and whenincorporated into the polymer introduces side groups comprisingfunctional groups that are pendant to the polymer chain. Functionalcomonomers which may be useful in this invention include fluorinated andperfluorinated monomers. Fluorinated monomers contain at least onefluorine atom. Perfluorinated monomers have at least one fluorine atom,and no carbon-hydrogen bonds and no carbon-halogen bonds other thancarbon-fluorine bonds. Suitable functional monomers have the generalformulae given in Table 1 where Z is defined as the functional group,examples of which are provided in Table 2.

TABLE 1 General structural formulae for comonomers CX₂═CXZ X: H,halogen, alkyl, fluoro alkyl CX₂═CX—R—Z X: H, halogen, alkyl, fluoroalkyl R: alkyl, alkyl ether, fluoro alkyl ether, perfluoro alkyl etherCF₂═CF—O—R_(f)—Z R_(f): fluoro alkyl or fluoro alkyl ether

Functional groups which may be incorporated into the copolymers aspendant groups, include but are not limited to the functional groupslisted in Table 2. As used herein, the term functional groupspecifically excludes ether groups (C—O—C), and groups formed bycarbon-halogen or carbon-hydrogen bonds. These bonds are described as—CX₂— or —CX₃ where X is either halogen or hydrogen. For purposesherein, while chemical moieties including ether groups, and chemicalmoieties formed from carbon-halogen bonds and carbon-hydrogen bonds, arenot considered functional groups, they may be part of a functionalcomonomer comprising a functional group that is suitable for use herein.

TABLE 2 Functional groups alcohols —C—OH aldehydes —CHO ketones —C═Ocarboxylic acids —COOH or salts esters —COOR, —OCOR where R is alkyl oraryl group cyano or nitriles —C≡N amines —C—NH₂, —C—RNH, —C—R₂NR₁,—C—R₁R₂R₃N+ where R, R₁, R₂ and R₃ are alkyl or fluoroalkyl amide

carbonyl halide —XC═O where X is F or Cl sulfonyl halide —SO₂X where Xis F or Cl sulfonic acid —SO₃H or salts sulfonamide —SO₂NH₂ sulfonimide—SO₂—NHN—SO₂— anhydrides —C(O)—O—(O)C— carbamates O═CONH— sulfides C—S—Cdisulfides C—SS—C cyanate —OC≡N phosphonic acid or salts O—P(═O)OH₂triazine

amidine —C(═NH)—NH2 isocyanate —N═C═OOther functional groups include but are not limited to sulfate ester,phosphate ester, thiol, imide, carbodiimide, imidazole, azide, azido,styrene, alkyl benzene, phenol, catechol, and the like.

Another aspect of this invention includes a process for reacting theexpanded functional TFE copolymer comprising pendant functional groupswhere at least some of the initial pendant functional groups that resultfrom the polymerization process, form secondary functional groups thatare different from the initial pendant functional groups as depicted inFIG. 4. In one embodiment, as depicted in FIG. 4, a group substitutionis depicted as Y being substituted for the functional group R. Furtherreactions of the secondary functional groups are possible and in someembodiments, for example, may form tertiary functional groups on theexpanded TFE copolymer material to further change the nature of anexpanded functional TFE copolymer material, e.g. to obtain a desiredchemical property.

The general formulae for comonomers of this invention are given inTable 1. The concentration of the comonomer containing a functionalgroup in the resulting functional TFE copolymers may be less than 5 mol%, or less than 3 mol %, or less than 2 mol %, or less than 1 mol % orless than 0.5 mol %. The concentration of comonomer having a functionalgroup in the resulting functional TFE copolymers may be greater than0.015 mol %, greater than 0.04 mol %, greater than 0.07 mol %, greaterthan 0.1 mol %, greater than 0.5 mol %, greater than 1.0 mol %, greaterthan 2 mol %, or greater than 3 mol %.

The concentration of comonomer containing a functional group in theresulting functional TFE copolymers may be between 0.01 and 5 mol %,0.01 and 3 mol %, or 0.01 and 2 mol %, and can be measured according tothe methods described herein.

At least one functional comonomer may be polymerized with TFE to providea copolymer having a multiplicity of pendant functional groups. Morethan one functional comonomer may also be provided. Where more than onefunctional comonomer is provided, the functional comonomers may providethe same or different functional groups that are pendant to the polymerchain. Additionally, one or more non-functional comonomers may becopolymerized with TFE and the at least one functional comonomer to formthe expandable functional TFE copolymers having pendant functionalgroups. Non-functional comonomers are defined herein as comonomers thatdo not result in pendant functional groups on the polymer chain.Non-functional comonomers include but are not limited to fluoro-olefinsi.e., hexafluoroproylene (HFP), fluoro alkyl vinyl ethers; PMVE(perfluoromethyl vinyl ether), PEVE (perfluoroethyl vinyl ether) andPPVE (perfluoropropyl vinyl ether).

In one embodiment, a functional comonomer comprises a fluorovinyl etherof the general formula

CF₂═CF—OR_(f)Z,

where R_(f) represents a fluoro alkyl group optionally interrupted byone or more oxygen(s) and Z represents a functional group from Table 2.Z may be cyano or nitrile, aldehyde, carboxylic acid or salt, ester,amine, amide, carbonyl halide, sulfonyl halide, sulfonic acid or salts,sulfonamide, sulfonimide, anhydride, sulfide, phosphonic acid or salt,hydroxyl (alcohol), sulfate esters, phosphate esters, isocyanate, thiol,imide, carbodiimide, imidazole, azide, azido, styrene, alkyl benzene,phenol, catechol, and the like. Fluorovinyl ether monomers may includecomonomers listed in Table 3.

TABLE 3 Fluoro Vinyl Ether Functional Comonomers Cyano vinyl ethersCF₂═CFOR_(f)—CN where R_(f) is a fluorinated alkyl or alkyl ether group.Illustrative examples are: CF₂═CF—O(CF₂)_(n)—CN where n = 2-12, orpreferably where n = 2-6; CF₂═CF—O[CF₂—CF(CF₃)—O]_(n)—CF₂—CF(CF₃)—CNwhere n = 0-4, or preferably where n = 0-2;CF₂═CF—[OCF₂CF(CF₃)]_(x)—O—(CF₂)_(n)—CN where x = 1-2, and n = 1-4; andCF₂═CF—O—(CF₂)_(n)—O—CF(CF₃)CN where n = 2-4. One preferred type ofmonomer includes perfluorinated polyethers having a nitrile group and atrifluorovinyl ether group, includingperfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene),CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CN. Sulfonyl fluoride vinyl ethersCF₂═CFOR_(f)SO₂F where R_(f) is a fluorinated alkyl or alkyl ethergroup. Illustrative examples are: CF₂═CFOCF₂CF₂SO₂F

One preferred sulfonyl fluoride-containing comonomer is perfluoro(3,6-dioxa-4-methyl-7-octane sulfonyl fluoride),

Acid or ester vinyl ether or other acid precursors

CF₂═CF—[OCF₂CF(CF₃)]_(m)—O(CF₂)_(n)—(CH₂)_(p)OCOR where R_(f) is afluorinated alkyl or alkyl ether group; m = 0-20; n = 1-10; p = 1-4; andR = alkyl. Illustrative examples are:CF₂═CF—[OCF₂CF(CF₃)]—O(CF₂)₂—CH₂COOCH₃ CF₂═CFO(CF₂)₃CH₂COOCH₃CF₂═CF—OCF₂CF(CF₃)OCF₂CF₂COOCH₃ CF₂═CFO(CF₂)₁₋₈COOCH₃CF₂═CFO(CF₂)₁₋₈COOC₂H₅ CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂COOCH₃

CF₂═CF—[OCF₂CF(CF₃)]—OCF₂CF₂COOH CF₂═CF—[OCF₂CF(CF₃)]—OCF₂CF₂CH₂OPO(OH)₂CF₂═CF[OCF₂CF(CF₃)]—OCF₂CF₂CH₂—OCONH₂ Hydroxyl vinyl ethersCF₂═CF(OCF₂CFCF₃)_(n)O_(p)(CF₂)_(m)CH₂OH where p = 0 or 1; m = 0-10; n =1-20; when m = 0, then p = 0,; and when m > 0, then p = 1. Illustrativeexamples are: CF₂═CF—O—CF₂CF(CF₃)OCF₂CF₂CH₂OH CF₂═CFOCF₂CF₂CF₂CH₂OH

Other comonomers suitable for use in making TFE copolymers describedherein include comonomers listed in Table 4.

TABLE 4 Other functional fluoro monomers CF₂═CFSO₂F CF₂═CFCF₂CF₂SO₂FCF₂═CFCF₂OCF₂CF₂SO₂F CF₂═CF(CF₂)₀₋₈COOCH₃ CF₂═CFCF₂OCF(CF₃)COOCH₃CF₂═CFCF₂OCF(CF₃)CF₂OCF(CF₃)COOCH₃ CF₂═CFCF₂O(CF₂)₄COOCH₃

The polymerization is carried out by an aqueous dispersionpolymerization process to produce a fine powder resin, by modifyingknown processes (e.g., U.S. Pat. No. 4,016,345 to Holmes). The additionof the functional comonomer or optionally other comonomers to thereaction vessel is controlled. Sufficient dispersing agent is introducedinto a water carrier where upon addition of TFE monomer in the presenceof a suitable polymerization initiator, and upon agitation and underautogenous TFE pressure of 10-40 kg/cm², polymerization proceeds untilthe desired level of colloidally dispersed functional TFE copolymerparticles is reached and the reaction is then stopped. The product ofthe polymerization reaction is the functional TFE copolymer dispersedwithin an aqueous colloidal dispersion.

In one embodiment, TFE monomer is pressurized into an autoclavecontaining water and polymerization initiators, along with paraffin waxto suppress coagulum formation, and an emulsifying agent. The additionof the functional comonomer or optionally other comonomers to thereaction is controlled. Where the comonomers are liquid, the processcomprises emulsifying the comonomers prior to adding the comonomers tothe reaction vessel. The comonomers are emulsified as emulsions in watercontaining a surfactant, preferably a fluoro surfactant.

Both the amount of functional comonomer added and the starting time ofthe comonomer addition, are determined based on the desiredconcentration of the comonomer in the resulting copolymer and thepolymerization reactivity of the comonomer. The step of adding thecomonomer, including the amount of comonomer added and the time in thepolymerization batch cycle at which the comonomer is added, iscontrolled to assure that the comonomer is essentially completelyreacted or consumed in the polymerization process before thepolymerization is about 80-90% complete. The step of continuingpolymerization, after essentially completely reacting or consuming thecomonomer in the polymerization process, consists of polymerizing TFEfor the final 10-20% of the polymerization in the absence of comonomer.This provides a functional TFE copolymer having high crystallinity ofthe material produced in the last 10-20% of the polymerization. Theresulting functional TFE copolymer resin is paste extrudable andexpandable into microporous structures.

In one embodiment, the process includes removing the comonomer prior to80% to 90% completion of the polymerization, by for example, evacuatingthe comonomer at low pressure or by steam assisted distillation.Subsequently, the polymerization of TFE is resumed and completed.

After polymerization is complete, the process further comprisescollecting the aqueous dispersion of particles which comprises the stepsof lowering the temperature to about 20° C., removing it from wax, andremoving it from the polymerization vessel. The aqueous dispersion isremoved from the polymerization vessel, diluted with water andcoagulated into fine powder by methods known in the art. The fine powderis dried in air or under vacuum at 100 to 200° C. prior to processing bypaste extrusion and expansion.

In one embodiment a blend of functional expandable TFE copolymer may becomprised of a functional expandable TFE copolymer mixed with anotherTFE copolymer having a different concentration of functional comonomer,or different type of functional comonomer, or with a homopolymer of TFEor a modified TFE polymer. Expandable polymers suitable for blendingwith the functional expandable TFE copolymers include but are notlimited to PTFE and polymers as described in U.S. Pat. No. 5,708,044(Branca, 1998), U.S. Pat. No. 6,541,589 (Baillie, 2003), U.S. Pat. No.7,531,611 (Sabol et al., 2009), U.S. patent application Ser. No.11/906,877 (Ford), and the like.

In another embodiment the functional expandable TFE copolymer is blendedwith a melt processable perfluoropolymer or fluoropolymer, or any otherpolymer, or combinations thereof, through any conventional methodincluding those taught in U.S. Pat. No. 6,127,486 to Burger et al. Otherpolymers that may be blended with the functional expandable TFEcopolymers include but are not limited to FEP, PFA, PVDF, ionomers,fluoroelastomers, and the like.

The blend of polymers may be mixed through a co-coagulated process fromdispersion, or blended in resin or fine powder form. The type and/ orconcentration of the components of the blend may be selected to provideddesirable mechanical, functional or processing properties. For example,the components of a blend may be selected to provide a material that canbe processed into a desired final material having desired functional andmechanical properties. Filler material, such as carbon, silica, and thelike, may also be combined with the functional expandable TFE copolymerthrough any conventional method including those as taught in U.S. Pat.No. 3,953,566to Gore, U.S. Pat. No. 4,187,390 to Gore and U.S. Pat. No.4,985,296 to Mortimer. In one embodiment, filler material is reactedwith the pendent functional groups of the expandable TFE copolymerdescribed herein. The filler material may be reacted prior to or afterthe expandable TFE copolymer is expanded.

Known paste-forming techniques can be used to convert the polymer resinto paste form into an article that can then be expanded after removing alubricant. The steps in paste-forming processes include mixing the resinwith a lubricant such as odorless mineral spirits and carrying outforming steps in which the resin is subject to shear.

The paste extrudable functional TFE copolymers made herein areexpandable to microporous structures characterized by having nodesinterconnected by fibrils, for example, by processes taught in U.S. Pat.No. 3,953,566 to make microporous expanded PTFE. Other processes forexpanding the paste extruded resin include but are not limited to thosemethods that are described in commonly owned U.S. Pat. No. 4,902,423, toBacino, U.S. Pat. No. 5,476,589 to Bacino, U.S. Pat. No. 5, 814,405 toBranca et al., and U.S. Pat. No. 7,306,729 to Bacino et al.

In one embodiment a composite membrane comprises an expanded functionalTFE copolymeric material having a microstructure characterized by nodesinterconnected by fibrils wherein the copolymer is a TFE copolymerhaving functional groups pendant to the polymer chain, and anothermaterial imbibed at least partially thereto. The imbibed material may bea polymer, such as but not limited to an elastomer, or thermoplastic, orthermoset, or may include an organic material such as but not limited tobiological material. In one embodiment the composite comprises an ionexchange material imbibed into the expanded material, such as taught inU.S. Pat. No. 6,254,978 to Bahar et al. In some embodiments the imbibedmaterial substantially occludes the pores of the expanded material asdetermined by the composite having a Gurley time of greater than 200seconds, as measured using the method described herein. In anotherembodiment the imbibed material is imbibed throughout the thickness ofthe expanded TFE copolymer described herein. In yet another embodimentthe imbibed material is reacted with the pendant functional groups ofthe expanded material. The imbibed material may be cross-linked with orcovalently bonded to the pendant functional groups using standardcross-linking chemistries know in the art. For example, a perfluorinatedsulfonyl fluoride resin can be reacted with ammonia or other amines toform a sulfonamide group. The sulfonamide groups can be crosslinked forexample by exposure to elevated temperatures, to form sulfonimidegroups.

Dense articles may be formed from expanded TFE copolymer materialsaccording to the methods describing in commonly owned US Pub. No.2008/0061472 to Kennedy et al.

In one embodiment, an expanded functional TFE copolymeric material isformed having a microstructure characterized by nodes interconnected byfibrils wherein the copolymer is a TFE copolymer, and wherein thecomonomer comprises functional groups which, in the copolymer, arependant to the polymer chain. The pendant functional groups can impartdifferent properties to the TFE copolymers. Expanded functional TFEcopolymers, and articles made therefrom, may undergo reactions such aschemical reactions with chemical reactants or reagents to react orchange the functional groups to impart different chemical or physicalproperties to the expanded article. Reactants, include include but arenot limited to organic material, bioactive species, spacer arms, imbibedmaterials, filler materials, synthetic polymers, perfluoropolymers,fluoropolymers, ion exchange materials, elastomers, functional TEEcopolymers described herein, and the like.

Another aspect of this invention includes a process for reacting theexpanded functional TFE copolymer comprising pendant functional groupswhere at least some of the initial pendant functional groups that resultfrom the polymerization process, form secondary functional groups thatare different from the initial pendant functional groups, as depicted inFIG. 4. Further reactions of the secondary functional groups arepossible and in some embodiments, for example, may form tertiaryfunctional groups on the expanded TFE copolymer material to furtherchange the nature of an expanded functional TFE copolymer material, e.g.to obtain a desired chemical property.

Organic and biochemistry reactions with the pendant functional groupsdescribed in Table 2 may include reactions between at least some of theinitial pendant functional groups to form secondary functional groups.For example, in one embodiment, a crosslinking reaction comprising thereaction of an expanded functional TFE copolymer comprising threeinitial pendant nitrile groups (—CN) upon heating to a temperature above250° C. forms a triazine structure resulting in crosslinking of the TEEcopolymeric material.

In a further embodiment, at least some of the initial pendant functionalgroups are chemically reacted with another chemical to form secondaryfunctional groups. For example, initial pendant functional groups suchas amide functional groups, acid halide functional groups, and nitrilegroups, are reacted with water to form acids as secondary functionalgroups, according to the following reactions.

—COOR+H₂O→—COOH where R is alkyl or fluoroalkyl;

—CONH₂+H₂O→—COOH;

—COX+H₂O→—COOH where X is halogen;

—SOOF+H₂O→—SOOOH; and

—CN+H₂O→—COOH

Additional chemical reactions include the reaction of initial pendantnitrile functional groups with ammonia to form amidine groups assecondary functional groups, for example by the following reaction.

—CN+NH₃→—C(═NH)NH₂

In one example an expanded functional TFE copolymer having pendantfunctional groups comprising an initial ester group can be reacted withother esters to form a secondary functional group in the form of adifferent ester group, according to the following reaction.

R₁—COOR+R₂—COOR′→R₁—COOR′+R₂—COOR

where R₁ is the initial functional TFE copolymer for example, TFE-EVE(CF₂═CF—OCF₂CF(CF₃)OCF₂CF₂COOCH₃) copolymer, R is alkyl or fluoroalkylgroup and R₂ is an alkyl or fluoroalkyl group and R′ is an alkyl orfluoroalkyl group different than R.

In addition, the monomers listed in Table 2 can be reacted using methodsthat are well know in the art, including but not limited totransamidation, isocyanurate formation, uret formation, dehydrogenationand unsaturation formation, hydrolysis, aminolysis, condensation,electrophilic addition, nucleophilic substitution, elimination, hydrogenabstraction, Michael's addition, and the like.

Where the expanded functional TFE copolymer comprises pendant estergroups and/or pendant acid functional groups, the initial functionalgroups may be reacted with ammonia or other amines to form amidesecondary functional groups, according to the following reactions.

—COOR+NH₃→—CONH₂

—COOH+NH₃→—CONH₂

where R is alkyl or fluoroalkyl.

Further, an expanded functional TFE copolymer comprising pendant nitrileinitial functional groups can be reacted to reduce the nitrile groups toamine secondary functional groups according to the following reaction.

—CN→—CH₂—NH₂

In another embodiment wherein the expanded functional TFE copolymercomprises pendant sulfonyl fluoride initial functional groups that canbe reacted with ammonia or other amines to form an expanded TFEcopolymer comprising sulfonamide secondary functional groups, theexpanded material can be further reacted to form sulfonimide tertiaryfunctional groups upon heating as follows.

—SOOF+NH₃—SO₂NH₂→—SO₂NHNSO₂—

In another embodiment, the functional TFE copolymer of the presentinvention may be treated with or exposed to radiation with or withoutthe presence of other reactant to change existing functional groups orcreate new functional groups. In one embodiment the functional TFEcopolymer material is exposed to radiation in the resin form and inanother embodiment it is exposed in the expanded form.

The expanded microporous TFE copolymer material containing pendantfunctional groups provide good media for chemical reactions. Because thefunctional groups are from comonomers polymerized with TFE, the pendantfunctional groups are integrated and may be distributed throughout themicrostructure of the expanded polymeric material. The pendantfunctional groups are surprisingly available for contact with each otheror with additional chemical reagents, reactants, organic material, orbioactive species. Moreover, the non-functional part of the expandedmicroporous structure has high fluorine concentration (equal to orgreater than 95 mol % TFE) which results in good chemical (solvent)resistance and stability at high temperatures which make the expandedfunctional copolymer material a good media for chemical reactions.

In a still further embodiment, the chemical reactants may includenatural and synthetic chemicals that are able to react with pendantfunctional groups of the expanded functional TFE copolymers. Naturalmaterials include biochemicals and biopolymers that include but are notlimited to carbohydrates, carbohydrate polymers or polysaccharides,chitin, glycogen, heparin, heparan sulfate, polypeptides and proteins,collagen, gelatin, enzymes, nucleic acids, DNA, RNA, lipids, steroids,hormones, pharmaceuticals, and other therapeutic agents.

The reactants may also include synthetic polymers. For both natural orbiopolymers and synthetic polymers, the reactive site of the reactantmay also be a functional group that is pendant to the reactant polymerchain. The reactive site of the reactant may alternatively be anon-pendant group. Synthetic polymeric reactants include but are notlimited to those listed in Table 5.

TABLE 5 Representative List of Synthetic Polymeric Reactants andFormulae TFE-PMVE-8CNVE copolymer—(CF₂—CF₂)—[CF₂—CF(OCF₃)]—CF₂—CFOCF₂CF(CF₃)OCF₂CF₂CN TFE-VDF-HFP-8CNVEcopolymer —(CF₂—CF₂)—(CH₂—CF₂)—[CF₂—CF(CF₃)]—CF₂—CFOCF₂CF(CF₃)OCF₂CF₂CNPoly(vinyl acetate) —[CH₂—CH(OCOCH₃)]— Poly(vinyl alcohol) —[CH₂CH(OH)]—Poly(ethylene glycol) HO—(CH₂—CH₂—O)_(n)—H Poly(propylene glycol)HO—(CH₂—CH₂—CH₂—O)_(n)—H Poly(ethylene imine) —(CH₂—CH₂—NH)— Poly(ethylacrylate) —[CH₂—CH(COOC₂H₅)]— Poly(acrylic acid) —[CH₂—CH(COOH)]—Poly(acrylonitrile) —[CH₂—CH(CN)]— Poly(ethylene vinyl acetate)—(CH₂—CH₂)_(m)—[CH₂—CH(OCOCH₃)]_(n)— Poly(ethylene vinyl alcohol)—(CH₂—CH₂)_(m)—[CH₂—CH(OH)]_(n)— Poly(acrylamide) —[CH₂—CH(CONH₂)]—Poly(n-butyl isocyanate) —[N(C₄H₉)—CO]— Poly(dimethylsiloxane)—[(CH₃)₂SiO]— Poly(lactic acid) —[O—CH(CH₃)—CO]— Poly(methacrylonitrile)—[CH₂—C(CH₃)(CN)]— Poly(L-lactide) —(CH₂—COO)—

In one embodiment, where the synthetic polymer comprises an —OH group,such as in poly(vinyl alcohol) (PVA), the material may be esterifiedwith a pendant functional —COOH group of the microporous expandedfunctional TFE copolymeric material to form ester bonds that connect thePVA and the microporous expanded material. In another embodiment, thependant functional —COOH group may be preactivated for example, to anacylimidazole using carbonyldiimidazole, which may then be esterifiedwith the PVA to form ester bonds that connect the PVA and themicroporous expanded material.

In another embodiment, a —CN group of a terpolymer made from TFE, PMVEand 8-CNVE (i.e., see Table 5) may be reacted with a pendant functional—CN group of the microporous expanded functional TFE copolymer materialto form triazine groups that crosslink the terpolymer with themicroporous expanded material. In a further embodiment, fluoroelastomersthat do not contain cyano functional groups may also be used to reactwith the pendant functional —CN group of the microporous expandedfunctional TFE copolymer material by adding triallylisocyanurate (TAIC)and peroxide to form crosslinking to improve the interface between thefluoroelastomer and the expanded microporous material.

Further, the expanded functional TFE copolymer may be reacted withbiochemical materials such as heparin, a polysaccharide. For example,where the biochemical material comprises hydroxyl —OH, sulfonic acid—SOOOH and carboxylic acid —COOH functional groups, the —OH group may bereacted with pendant carboxylic acid on a microporous expandedfunctional TFE copolymer material to form an ester. The —OH groups mayalso react with an ester group on the microporous material to form a newester group. The —SOOOH group may react with an amine group on themicroporous expanded functional TFE copolymer material to form asulfonamide or sulfonimide. The —COOH group on heparin may react with apendant functional —OH group on the expanded microporous functional TFEcopolymer material to form ester groups. A —COOH group from abiochemical material may also react with an amino group on themicroporous expanded functional TFE copolymer material to form amidegroups. A —CHO (aldehyde) group from a biochemical material may alsoreact with an amino group on the microporous expanded functional TFEcopolymer material to form imine groups. In one embodiment heparin isimmobilized to the resin or expanded polymeric material describedherein, and in some cases to the pendant functional group, by manymethods including those taught in U.S. Pat. No. 6,461,665 to Scholanderet al.

A broad array of natural and synthetic bioactive species and otherligands such as biochemicals or biopolymers, and pharmaceutically orbiologically active molecular compounds, or organic material can bereacted or otherwise immobilized to the functional group of a supportmember, as depicted in FIG. 3. A support member, as used herein refersto the functional TFE copolymer fine powder resin or expanded polymericmaterial comprising a functional TFE copolymer material as describedherein. As used herein, the terms immobilize, attach, and theirderivatives refer to adsorption, such as, physisorption orchemisorption, ligand/receptor interaction, covalent bonding, hydrogenbonding, or ionic bonding of a polymeric substance or a bioactivespecies to a support member. Bioactive species, as used herein, includeenzymes, organic catalysts, ribozymes, organometallics, proteins,glycoproteins, peptides, polyamino acids, antibodies, nucleic acids,steroidal molecules, antibiotics, antimycotics, cytokines,carbohydrates, oleophobics, lipids, extracellular matrix material and/orits individual components, dyes and fluorescent probes, colloidalmetals, pharmaceuticals, and therapeutics, for example. Cells, such as,mammalian cells, reptilian cells, amphibian cells, avian cells, insectcells, planktonic cells, cells from non-mammalian marine vertebrates andinvertebrates, plant cells, microbial cells, protists, geneticallyengineered cells, and organelles, such as mitochondria, are alsobioactive species. In addition, non-cellular biological entities, suchas viruses, virenos, and prions are considered bioactive species.Natural and synthetic polymers are also considered bioactive species,and may be attached to the support member to alter surface energetics,hydrophilicity, hydrophobicity and lubricity; to resist to proteinadsorption; to enhance affinity adsorption; and the like; examples ofsuch polymers include but are not limited to those listed in Table 5,and also include but are not limited to polyethylene glycol,polypropylene glycol, hyaluronic acid, alginic acid, heparin, heparansulfate, polyacrylamide, polyethyleneimine, dextran sulfate,cyclodextrin, agar, agarose, chitin, chitosan, polyvinylpyrrolidinone,polyvinyl alcohol, cellulose and its derivatives, starch polyaldehyde,polyhydroxyethyl methacrylate, silane and its derivatives, or anotherfunctional TFE copolymer as described herein, and the like.

A bioactive species may be immobilized to the functional TFE copolymerfine powder resin or expanded polymeric material comprising a functionalTFE copolymer material as described herein, by any conventional methodincluding those taught in U.S. Pat. No. 5,914,182 to Drumheller, U.S.Pat. No. 5,897,955 to Drumheller, U.S. Pat. No. 5,874,165 to Drumheller,U.S. Pat. No. 5,916,585 to Cook, et al. The bioactive species may beimmobilized to the resin or expanded polymeric material as describedherein without reaction to the pendant functional group, therein leavingthe functional group available for other reactions. In one embodimentthe bioactive species is immobilized to the resin or expanded polymericmaterial of the present invention through reaction directly to thependant functional group, as depicted in FIG. 3. In another embodimentan initial functional group on the support member is converted to asecond functional group different from the initial functional group asdepicted in FIG. 4, and the bioactive species is immobilized to thesecond functional group as depicted in FIG. 5. In yet another embodimentthe bioactive species is immobilized to the resin or expanded polymericmaterial of the present invention through an intermediate component thatis attached to the pendant functional group. The intermediate componentmay comprise a covalent bond between the species and the support member,or may comprise a spacer arm. A spacer arm is immobilized onto thepolymeric substrate in some cases, as depicted in FIG. 6, to enhance theyield of surface attachment, to minimize surface-induced steric effects,or to enhance receptor-ligand interactions. The spacer arm may behomobifunctional, homopolyfuntional, heterobifunctional,heteropolyfuntional, zero length, cleavable, photolytically labile, andthe like. The spacer arm, in one embodiment, may also comprise apolymeric surfactant, or a multifunctional copolymer, comprised of atleast one domain that has a physisorb or chemisorb affinity for theresin or expanded polymeric material of the present invention to allowphysisorption or chemisorption of the multifunctional copolymer onto thesurface of the resin or expanded polymeric material and at least oneother domain that is chemically reactive to allow covalentimmobilization of a bioactive species or allow cross-linking with asuitable cross-linking agent. The spacer arm may also comprise thefunctional expandable fluoropolymer having the function group listed inTable 2. The spacer arm may also comprise a first layer attached to thependant functional group and a second layer attached to the first layer.The spacer arm of the first layer may be the same or different than thespacer arm of the second layer.

A wide range of intermediate components, including spacer arms, could beused as taught in U.S. Pat. No. 5,914,182 to Drumheller, U.S. Pat. No.5,897,955 to Drumheller, U.S. Pat. No. 5,874,165 to Drumheller, U.S.Pat. No. 5,916,585 to Cook, et al.

Organic species including enzymes, cells and proteins, and spacer arms,may also be immobilized to the resin or expanded polymeric material asdescribed herein and in some cases to the pendant functional group, bymany methods including those taught in GT Hermanson, “BioconjugateTechniques”, 2nd Ed, Academic Press (Amsterdam), 2008, and specificallyin chapter 1-8, 13-15, 17-18, 22-27, Methods in Enzymology, “ImmobilizedEnzymes and Cells”, Part B, Vol 125, K. Mosbach (Ed), Academic Press(Orlando), 1987, and S S Wong, “Chemistry of Protein Conjugation andCross-Linking”, CRC Press (Boca Raton), 1993, specifically chapters 2-6and 12.

The bioactive species in one embodiment is also a spacer arm includingbut not limited to those listed in Table 5, and including but notlimited to polyalcohol such as polyvinyl alcohol; polyamine such aspolyethylenemine; polyether such as polyethylene glycol, polyaldehydesuch as starch polyaldehyde; polyester such as polyvinyl acetate;polycarboxylic acid such as polyacrylic acid; polyamide such aspolyvinylpyrrolidinone, polyaryl ketone, polyazide, polythiol,polybiotin, polyavidin, polysilane, polydopamine, polyquinone,polysaccharide such as heparin, heparan sulfate, polyamino acid,polynucleic acid, polyalkane, and the like. The spacer arm may behomofunctional, heterofunctional, zero length, cleavable, photolyticallylabile, and the like. In another embodiment two or more bioactivespecies are immobilized to the resin or expanded polymeric material ofthe present invention and in some embodiments one is immobilized to thefunctional pendant group and the other is not. In another embodiment thepolymeric material is a medical device. In another embodiment thepolymeric material is a component of a medical device.

As used herein, the term medical device includes but is not limited totemporarily implantable materials and devices such as catheters,balloons, wound dressings, and the like; permanent implantables such assutures, vascular grafts, stents, stent-grafts, patches, barriers, heartand vascular valves, tissue growth scaffolds, orthopedic devices, plugs,and the like, and non-implantables such as collection bags, dialysismedium, cell growth scaffolds, and the like. A medical device may alsoinclude ex vivo or in vitro materials and devices such as but notlimited to tubing, membranes, chromatography medium, adsorption medium,affinity medium, bioseparation and biopurification medium, biofilters,substrates for protein & DNA analysis, and the like. A medical devicemay also include fabrics, garments, and the like to protect againstdisease or pathogen transmission and the like. A medical device may alsobe essentially any type of medical device, or a component of a medicaldevice, that may be fabricated from the copolymers of the presentinvention.

Test Methods

Break Strength Test of Microporous ePTFE

A process for testing the break strength of a paste extruded andexpanded functional microporous TFE copolymer beading is provided. Thebreak strength associated with an extruded and expanded (stretched) TFEpolymeric beading produced from a particular resin is directly relatedto that resin's general suitability for expansion, and various methodshave been employed to measure break strength. The following procedurewas used to produce and test expanded beading specimens made from thecopolymers of this invention, the data for which are reported hereinbelow.

For a given resin, 113.4 g of fine powder resin is blended together with130 cc/lb (24.5 g) of Isopar® K. The blend is aged for about 2 hours at22° C. in a constant temperature water bath. A 2.54 cm diametercylindrical preform is made by applying about 1,860 kPa of preformingpressure for about 20 seconds. The preform is inspected to ensure it iscrack free. An extruded beading is produced by extruding the preformed,lubricated resin through a 0.254 cm diameter die having a 30 degreeincluded inlet angle. The extruder barrel is 2.54 cm in diameter and theram rate of movement is 50.8 cm/min. The extruder barrel and die are atroom temperature, maintained at 23° C., plus or minus 1.5° C. TheIsopar® K is removed from the beading by drying it for about 25 minutesat 225-230° C. Approximately the first and last 2.5 m of the extrudedbeading are discarded to eliminate end effects. A 5.0 cm section of theextruded beading is expanded by stretching at 290° C. to a final lengthof 127 cm (expansion ratio of 25:1) and at an initial rate of stretch of1000% per second, which is a constant rate of 50.8 cm per second.Approximately a 30 cm length from near the center of the expandedbeading is removed, and the maximum break load of the removed sampleheld at room temperature (23° C. plus or minus 1.5° C.) is measuredusing an Instron® tensile tester using an initial sample length of 5.0cm and a crosshead speed of 5.0 cm/min.

Measurements in duplicate are obtained and reported as the average valuefor the two samples. This procedure is similar to that described in U.S.Pat. No. 6,177,533B1.

Crystallinity Measurements of Expanded Membranes

Infrared spectra were obtained with a Nicolet 550 Series IIspectrometer. The expanded membrane samples were used and scanned for100 scans. The two peaks (about 2363 cm⁻¹ and 778 cm⁻¹) of interest wereused for crystallinity measurements. The degree of crystallinity wascalculated by using the following equation,

Crystallinity %=100−(H ₇₇₈/(H ₂₃₆₃×25))

where H₇₇₈ is the peak height near wavenumber 778 cm⁻¹ and H₂₃₆₃ thatnear wavenumber 2363 cm⁻¹. The baseline for the peak near 778 cm⁻¹ wasobtained from the line between 754 and 810 cm⁻¹. The baseline for thepeak near 2363 cm⁻¹ was obtained from the line between 2200 and 2600cm⁻¹.

Determination of Functional Groups

The Digilab FTS4000 infrared spectrometer was used to determinefunctional groups. FTIR spectra were obtained in the ATR mode by using aPike Technologies MIRacle ATR with a Ge crystal. Wavenumbers foridentifying specific functional groups are given in the examples below.

Determination of Compositions of Functional TFE Copolymers

NMR was used to quantify compositions of functional TFE copolymers. AllNMR measurements were carried out on a Bruker BioSpin Avance II 300 MHzspectrometer operating at a resonance frequency of 282.4 MHz forfluorine-19 with a pulse duration of 3 μs. Spectra were collected atabout 296 K on a Bruker-BioSpin 2.5 mm cross polarization magic anglespinning (CPMAS) probe positioned in a standard bore 7.05 T Bruker ultrashielded superconducting magnet. The samples were positioned at themagic angle and spun at 32.5 kHz. The sample weight for all experimentswas about 10 to 25 mg. The software used for data acquisition and dataprocessing was Topspin 1.3. The ¹⁹F chemical shifts were externallyreferenced to the CF₂ signal of PTFE at −123 ppm.

Thickness Measurements

Thickness was measured by placing the material between the two plates ofa Kafer FZ1000/30 thickness snap gauge (Käfer Messuhrenfabrik GmbH,Villingen-Schwenningen, Germany). The average of the three measurementswas used.

Density Measurements

Density was used to calculate the percent porosity of expanded materialsusing 2.2 g/cc as the full density of the sample. Samples die cut toform rectangular sections 2.54 cm by 15.24 cm were measured to determinetheir mass (using a Mettler-Toledo analytical balance modelAG204) andtheir thickness (using a Kafer FZ1000/30 snap gauge). Using these data,density was calculated with the following formula:

$\rho = \frac{m}{w*l*t}$

in which: ρ=density (g/cc); m=mass (g); w=width (cm); l=length (cm); andt=thickness (cm). The average of the three measurements was used.

Tensile Break Load Measurements and Matrix Tensile Strength (MTS)Calculations

Tensile break load was measured using an INSTRON 1122 tensile testmachine equipped with flat-faced grips and a 0.445 kN load cell. Thegauge length was 5.08 cm and the cross-head speed was 50.8 cm/min. Thesample dimensions were 2.54 cm by 15.24 cm. For longitudinal MTSmeasurements, the larger dimension of the sample was oriented in themachine, or “down web,” direction. For the transverse MTS measurements,the larger dimension of the sample was oriented perpendicular to themachine direction, also known as the cross web direction. Each samplewas weighed using a Mettler Toledo Scale Model AG204, then the thicknessof the samples was taken using the Kafer FZ1000/30 thickness snap gauge.Three samples were then tested individually on the tensile tester. Theaverage of the three maximum load (i.e., the peak force) measurementswas used. The longitudinal and transverse MTS were calculated using thefollowing equation:

MTS=(maximum load/cross-section area)*(density of PTFE)/density of thesample),

wherein the density of PTFE is taken to be 2.2 g/cc.

Bubble Point Measurements

The bubble point and mean flow pore size were measured according to thegeneral teachings of ASTM F31 6-03 using a Capillary Flow Porometer(Model CFP 1500 AEXL from Porous Materials Inc., Ithaca, N.Y.). Thesample membrane was placed into the sample chamber and wet with SilWickSilicone Fluid (available from Porous Materials Inc.) having a surfacetension of 19.1 dynes/cm. The bottom clamp of the sample chamber had a2.54 cm diameter, 3.175 mm thick porous metal disc insert (MottMetallurgical, Farmington, Conn., 40 micron porous metal disk) and thetop clamp of the sample chamber had a 3.175 mm diameter hole. Using theCapwin software version 6.62.1 the following parameters were set asspecified in the table below. The values presented for bubble point andmean flow pore size were the average of two measurements.

Parameter Set Point maxflow (cc/m) 200000 bublflow (cc/m) 100 F/PT (oldbubltime) 40 minbppres (PSI) 0 zerotime (sec) 1 v2incr (cts) 10 preginc(cts) 1 pulse delay (sec) 2 maxpre (PSI) 500 pulse width (sec) 0.2mineqtime (sec) 30 presslew (cts) 10 flowslew (cts) 50 eqiter 3 aveiter20 maxpdif (PSI) 0.1 maxfdif (cc/m) 50 sartp (PSI) 1 sartf (cc/m) 500

Gurley Measurements

The Gurley air flow test measures the time in seconds for 100 cm³ of airto flow through a 6.45 cm² sample at 12.4 cm of water pressure. Thesamples were measured in a Gurley Densometer Model 4340 AutomaticDensometer. The average of the three measurements was used.

The following examples are intended to be illustrative of the invention,but are not to be construed as limiting the scope of the invention inany way.

EXAMPLE 1

A fine powder resin comprising the copolymer of TFE and 8-CNVE wasprepared as follows.

To a 50-liter, horizontal polymerization reactor equipped with a3-bladed agitator was added 1.5 kg of paraffin wax, 28 kg of de-ionized(DI) water, 18 g of ammonium perfluorooctanoic acid (APFO) and 5 g ofsuccinic acid dissolved in about 50 g of DI water. The reactor andcontents were heated above the melting point of the wax. The reactor wasrepeatedly vacuumed and pressurized (to about 1 atmosphere or less) withTFE until the oxygen level was reduced to 20 ppm or less. The contentswere briefly agitated at about 60 rpm between vacuum and purge cycles toensure that the water was deoxygenated. 35 g ofperfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene) (8-CNVE)(CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CN), 5 g of 20% APFO, 250 g of DI water wereemulsified by Omni Mixer Homogenizer. To the reactor under vacuum wasadded the above 8-CNVE emulsion as a precharge of comonomer, and thereactor was heated to 83° C. TFE was then added to the reactor until thepressure reached 2.8 MPa, and KMnO₄ in DI water solution (0.063 g/L) wasinjected at 80 ml/min. until about 4 kg of TFE had been added. This wasaccomplished in about 64 minutes. About 320 ml of 20% APFO solution wasadded in 40 ml increments, the first increment being added after about 1kg of TFE had been added to the reactor, and the subsequent incrementsadded after each subsequent 1 kg of TFE had been added, so that thefinal increment was added after 9 kg of TFE had been charged. The KMnO₄addition rate was decreased to 40 ml/min at the 4 kg TFE level andcontinued at this rate until about 6 kg of TFE had been added, at whichtime the addition of KMnO₄ was stopped.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 49.9 kg, and thesolid content of the dispersion was 32.1 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.175 micron.

The polymer dispersion was diluted to about 15 wt % with DI water andthen coagulated with diluted nitric acid (300 ml 65% nitric acid dilutedwith 700 ml DI water) at about 16° C. The ratio of the diluted polymerdispersion to nitric acid was 20 kg dispersion per 100 ml diluted nitricacid. The agitation speed for coagulation was about 275 rpm. Thecoagulum was dried at 130° C. for 18 hours under vacuum. Solid-state ¹⁹FNMR was carried out to characterize the composition of the polymer. Thispolymer contains 0.017 mol % (0.064 wt %) 8-CNVE. The break strength ofthe beading was approximately 42 newtons (N).

EXAMPLE 2

A fine powder resin comprising the copolymer of TFE and 8-CNVE wasprepared as follows.

The procedures for Example 1 were repeated except that the concentrationof the KMnO₄ solution was 0.1 g/L. The KMnO₄ solution was injected at 80ml/min. until about 4 kg of TFE had been added. This was accomplished inabout 38 minutes. Then the KMnO₄ addition rate was decreased to 40ml/min and continued at this rate until about 6 kg of TFE had beenadded, at which time the addition of KMnO₄ was stopped. The totaladdition time of KMnO₄ solution was about 43 minutes.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 49.2 kg, and thesolid content of the dispersion was 34.5 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.208 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 130° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 0.019 mol % (0.072) wt % 8-CNVE.

EXAMPLE 3

A fine powder resin comprising the copolymer of TFE and 8-CNVE wasprepared as follows.

The procedures for Example 1 were repeated except that 52 g 8-CNVE wasadded to 5g of 20% APFO and 250 g of Dl water, emulsified by Omni MixerHomogenizer, and added as a precharge to the reaction. The concentrationof the KMnO₄ solution was 0.1 g/L. The KMnO₄ solution was injected at 80ml/min until about 3 kg of TFE had been added. This was accomplished inabout 63 minutes. Then the KMnO₄ addition rate was decreased to 40ml/min and continued at this rate until about 4 kg of TFE had beenadded. The KMnO₄ addition rate was again increased to 80 ml/min andcontinued at this rate until about 6 kg of TFE had been added, at whichtime the addition of KMnO₄ was stopped. The total addition time of KMnO₄solution was about 86 minutes.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 52.2 kg, and thesolid content of the dispersion was 32.8 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.186 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 130° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 0.044 mol % (0.17 wt %) 8-CNVE. The break strengthof the beading was 45 N.

EXAMPLE 4

A fine powder resin comprising the copolymer of TFE and 8-CNVE wasprepared as follows.

The procedures for Example 1 were substantially repeated except that 118g 8-CNVE was added to 5g of 20% APFO and 250 g of DI water, emulsifiedby Omni Mixer Homogenizer, and added as a precharge to the reaction. Theconcentration of the KMnO₄ solution was 0.15 g/L. The KMnO₄ solution wasinjected at 80 ml/min until about 2 kg of TFE had been added, at whichtime the addition of KMnO₄ was stopped. The total addition time of KMnO₄solution was about 143 minutes. 10.4 kg of KMnO₄ solution was added.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 13.4 kg of TFE had been added to thereactor. The weight of the dispersion produced was 52.8 kg, and thesolid content of the dispersion was 27.9 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.194 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 130° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 0.13 mol % (0.51 wt %) 8-CNVE. The break strengthof the beading was 47 N.

EXAMPLE 5

A fine powder resin comprising the copolymer of TFE and PSVE wasprepared as follows.

To a 50-liter, horizontal polymerization reactor equipped with a3-bladed agitator was added 1.5 kg of paraffin wax and 28 kg of DIwater, 18 g of APFO and 5 g of succinic acid dissolved in about 50 g ofDI water. The reactor and contents were heated above the melting pointof the wax. The reactor was repeatedly vacuumed and pressurized (toabout 1 atmosphere or less) with TFE until the oxygen level was reducedto 20 ppm or less. The contents were briefly agitated at about 60 rpmbetween vacuum and purge cycles to ensure that the water wasdeoxygenated. 1500 g of perfluoro(8-sulfonic acidfluoride-5-methyl-3,6-dioxa-1-octene) (PSVE)(CF₂═CFOCF₂—CF(CF₃)OCF₂CF₂SOOF), 50 g of 20% APFO, and 1500 g of DIwater were emulsified by Omni Mixer Homogenizer. To the reactor undervacuum 688 g of the above PSVE emulsion was added as a precharge ofcomonomer, and the reactor was heated to 83° C. TFE was then added tothe reactor until the pressure reached 2.8 MPa, and KMnO₄ in DI watersolution (0.063 g/L) was injected at 80 ml/min. until about 4 kg of TFEhad been added. A drop in pressure indicated the start ofpolymerization. TFE was continuously added to maintain the pressure.About 320 ml of 20% APFO solution was mixed with the rest of the PSVEsolution. The mixed solution was added with an increment of 43 ml for200 g of TFE consumed. The first increment was added after about 200 gof TFE had been added to the reactor, and the subsequent increments wereadded after each subsequent 200 g of TFE had been added. The finalincrement was added after 12 kg of TFE had been charged. The KMnO₄addition rate was decreased to 40 ml/min at the 4 kg TFE level andcontinued at this rate until about 10 kg of TFE had been added, at whichtime the addition of KMnO₄ was stopped. This was accomplished in about47 minutes.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 50.5 kg, and thesolid content of the dispersion was 36.6 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.270 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 130° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 1.9 mol % (8.0 wt %) PSVE. The break strength ofthe beading was 28.5 N.

EXAMPLE 6

A fine powder resin comprising the copolymer of TFE and EVE was preparedas follows.

To a 50-liter, horizontal polymerization reactor equipped with a3-bladed agitator was added 1.5 kg of paraffin wax, 28 kg of DI water,18 g of APFO and 5 g of oxalic acid dissolved in about 50 g of DI water.The reactor and contents were heated above the melting point of the wax.The reactor was repeatedly vacuumed and pressurized (to about 1atmosphere or less) with TFE until the oxygen level was reduced to 20ppm or less. The contents were briefly agitated at about 60 rpm betweenvacuum and purge cycles to ensure that the water was deoxygenated. 80 gof perfluoro(8-carboxymethyl-5-methyl-3,6-dioxa-1-octene) (EVE)(CF₂═CF—OCF₂CF(CF₃)OCF₂CF₂COOCH₃), 5 g of 20% APFO, and 250 g of DIwater were emulsified by Omni Mixer Homogenizer. To the reactor undervacuum was added the above EVE emulsion as a precharge of comonomer, andthe reactor was heated to 83° C. TFE was then added to the reactor untilthe pressure reached 2.8 MPa, and KMnO₄ in DI water solution (0.15 g/L)was injected at 80 ml/min until about 1 kg of TFE had been added. Apressure drop indicated that polymerization started. TFE wascontinuously added to maintain the pressure. After 1 kg of TFE wasadded, the injection rate of KMnO₄ in DI water solution was decreased to40 ml/min until 3 kg of TFE had been added and then the solution wasinjected at 20 ml/min. Until about 6 kg of TFE had been added, at whichtime the addition of KMnO₄was stopped. This was accomplished in about 15minutes. About 320 ml of 20% APFO solution was added in 40 mlincrements, the first increment being added after about 2 kg of TFE hadbeen added to the reactor, and the subsequent increments were addedafter each subsequent 1 kg of TFE had been added, so that the finalincrement was added after 9 kg of TFE had been charged.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 45.6 kg, and thesolid content of the dispersion was 35.1 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.232 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 180° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 0.098 mol % (0.41 wt %) EVE. The break strength ofthe beading was 23.6 N.

EXAMPLE 7

A fine powder resin comprising the copolymer of TFE and EVE was preparedas follows.

The procedures for Example 6 were substantially repeated except that thereactor was evacuated after 10 kg of TFE had been added into the reactorand then TFE was recharged into the reactor until the pressure of thereactor was 2.8 MPa. Then, the KMnO₄ solution was injected at 80 ml/min.until about 1 kg of TFE had been added. Then the KMnO₄ addition rate wasdecreased to 40 ml/min and after 2 kg of TFE was added, the KMnO₄injection rate was decreased to 20 ml/min until 6 kg of TFE had beenadded, at which time the addition of KMnO₄ was stopped. The totaladdition time of KMnO₄ solution was about 31 minutes.

The polymerization reaction was then allowed to continue and thereaction was stopped after about 16 kg of TFE had been added to thereactor. The weight of the dispersion produced was 46.2 kg, and thesolid content of the dispersion was 35.4 wt %. The raw dispersionparticle size (RDPS) of the polymer particles was 0.238 micron.

The dispersion was coagulated in the same process as described inExample 1 and dried at 180° C. for 18 hours under vacuum. Solid-state¹⁹F NMR was carried out to characterize the composition of the polymer.This polymer contains 0.095 mol % (0.40 wt %) EVE. The break strength ofthe beading was 28.0 N.

EXAMPLE 8

An expanded functional copolymer comprising the copolymer of TFE and8-CNVE was prepared as follows.

The resin from Example 3 was mixed with Isopar® K (Exxon Mobil Corp.,Fairfax, Va.) at a concentration of 0.217 g/g of resin and formed into apellet approximately 10 cm in diameter at a pressure of about 2070 kPa.The pellet was heated to about 50° C. and paste extruded into a tapehaving dimensions of about 0.076 cm thick and about 15.25 cm widethrough a die having a reduction ratio of about 100 to 1, at a averageextrusion pressure of about 10,300 kPa. The reduction ratio is the ratioof the cross sectional area of the extruder barrel to the crosssectional area of the extrusion die exit. The resultant tape wascalendared at a rate of 50 meters/minute at about 45° C. to about 0.020cm thick and about 15.25 cm wide. The lubricant was removed by heatingat 180° C. to 210° C. The width of the dried tape was about 14.6 cm.

The resultant tape was stretched in the longitudinal direction at about300° C. and 4.5 meters/minute to a ratio of 10:1. The resultant tape wasabout 8.9 cm wide. The resultant tape was stretched transversely at 300°C. at 19.8 meters/minute at a ratio of 7.5:1 and sintered at about 390°C. for about 20 seconds. The resultant membrane was characterized andthe results are given in Table 6. A scanning electron micrograph, at10,000 magnification, of the membrane is given in FIG. 1.

TABLE 6 Properties of Membrane Made in Example 8 Example 8 (fine powderproduced in Example 3) Porosity (%) 85 Mean Flow Pore size (μm) 0.16Thickness (μm) 2.5 Density (g/cc) 0.39 Crystallinity (%) 71 Avg. MatrixTensile 230 Strength (MPa)

EXAMPLE 9

An expanded functional copolymer comprising the copolymer of TFE andPSVE was prepared as follows.

A resin made in accordance with Example 5 containing 0.76 mol % (3.3 wt%) PSVE was both paste extruded into a tape and stretched in accordancewith the processes of Example 8 except that the lubricant was removed byheating at about 250° C. The extruded tape had a width of about 13 cmand then the tape was paste stretched into a microporous membrane. Theresultant membrane was characterized and the results are given in Table7. A scanning electron micrograph, at 10,000 magnification, of themembrane is given in FIG. 2.

TABLE 7 Properties of Membrane Made in Example 9 Example 9 Mass/area(g/m²⁾ 4.1 Thickness (μm) 2.5 Gurley (sec) 9.6 Bubble Point (kPa) 630Avg. Matrix Tensile Strength (MPa) 230

EXAMPLE 10

An expanded functional copolymer comprising the copolymer of TFE and8-CNVE was reacted as follows.

An expanded microporous functional TFE copolymer membrane was madeaccording to Example 8, from a PTFE fine powder prepared according tothe process described in Example 3 containing 0.044 mol % (0.17 wt %)8CNVE. The expansion process, carried out at about 300° C. and thenrestrained and heated at about 390° C. in an oven for about 20 seconds,resulted in an expanded microporous membrane containing triazine (about1560 cm⁻¹), a crosslinked structure, and the unreacted cyano group(about 2297 cm⁻¹) determined by FTIR.

EXAMPLE 11

An expanded functional copolymer comprising the copolymer of TFE and8-CNVE was reacted as follows.

Aminopropyltriethoxysilane (Aldrich) was mixed with a 95 wt % ethanol(Aldrich)/5 wt % DI water solution to yield a 10 wt % silane solution.About five minutes were allowed for hydrolysis and forming the silanolgroups. An expanded functional TFE copolymer membrane made according toExample 8 from a TFE copolymer fine powder containing 0.044 mol % (0.17wt %) 8-CNVE was immersed in the solution for 2 minutes. It was thenrinsed free of excess silane solution by dipping briefly in ethanol andair dried. Curing of the membrane was carried out at 110° C. for 30 min.The reacted membrane, became transparent in water, indicating it washydrophilic. The unreacted membrane was white in water, indicating itwas hydrophobic. A hydrophilic membrane as described herein will exhibitwater penetration into the pores of the expanded membrane after exposureto water, including surface exposure to water or submerging in water.

EXAMPLE 12

An expanded functional copolymer comprising the copolymer of TFE and8-CNVE was reacted as follows.

An expanded functional TFE copolymer membrane made according to Example8 from a TFE copolymer fine powder containing 0.044 mol % (0.17 wt %)8-CNVE prepared in Example 3 was first wetted with isopropanol (IPA)(Aldrich) and then immersed in a 28 wt % aqueous ammonium hydroxidesolution (Aldrich) at room temperature for 20 hours. It was then rinsedwith DI water and air dried. The reacted expanded functional TFEcopolymer membrane contains a new group, amidine (about 1743 cm⁻¹),determined by FTIR.

EXAMPLE 13

An expanded functional copolymer comprising the copolymer of TFE and8-CNVE was cross linked with a fluoroelastomer.

Viton™ GF-S (fluoroelastomer) was compounded with 4 phrtriallylisocyanurate (Aldrich) and 4 phr Luperox™ 101 (Aldrich) on amill; the compounded mixture was dissolved in MEK (methyl ethyl ketone)to form a 20% solids solution. An expanded functional TFE copolymermembrane was made according to Example 8 from a TFE copolymer finepowder made according to the process of Example 3 containing 0.044 mol %(0.17 wt %) 8-CNVE. The membrane was imbibed with the Viton™ compoundand dried at 90° C. Slabs (composite A) having a thickness of about 0.5to 0.76 mm were made by stacking Viton™ imbibed expanded functional TFEcopolymer membrane. Expanded functional TFE copolymer/Viton™ compositewas formed by molding at 180° C. for 10 min followed by post-curing in aconvection oven at 233° C. for 24 hours. Comparative slabs (composite B)were made by a similar process, except that ePTFE membrane was used inplace of expanded functional TFE copolymer membrane and therefore, didnot contain 8-CNVE. The IMASS peel tester was used for peel tests thatwere carried out in the T-peel mode with a 5-lb load cell at a speed of6 in/min. Peel strengths were 2.2 and 1.5 lb/in for composite A andcomposite B, respectively.

EXAMPLE 14

An expanded functional copolymer comprising the copolymer of TFE andPSVE was reacted as follows.

An expanded functional TFE copolymer membrane made by the processingconditions of Example 9, was made from a functional TFE copolymer finepowder containing 1.9 mol % (8.0 wt %) PSVE made according to theprocess of Example 5. The membrane was first wetted with IPA and thenimmersed in a 20 wt % KOH solution (Aldrich) at 100° C. for 24 hours. Itwas then rinsed with DI water and was immersed in 15 wt % nitric acid(Aldrich) at 60° C. for 24 hours. The reacted membrane was rinsed withDI water and dried at 100° C. for 1 hour. The conversion of the sulfonylfluoride group (about 1469 cm⁻¹) into the sulfonic acid group (about1059 cm⁻¹) was confirmed by FTIR.

EXAMPLE 15

An expanded functional copolymer comprising the copolymer of TFE andPSVE was reacted as follows.

An expanded functional TFE copolymer membrane made by the processingconditions of Example 9, was made from a functional TFE fine powdercontaining 1.9 mol % (8.0 wt %) PSVE made according to the process ofExample 5. The membrane was first wetted with IPA and then immersed in a28 wt % aqueous ammonium hydroxide solution at about 5° C. for 3 hours.The reacted membrane was rinsed with DI water and air dried. Theexpanded functional TFE copolymer membrane was cured by heating at 200°C. for 1 hour. The sulfonimide group (about 1740 cm⁻¹), the crosslinkedstructure, was determined by FTIR.

EXAMPLE 16

An expanded functional copolymer comprising the copolymer of TFE and EVEwas reacted as follows.

Expanded functional TFE copolymer membrane was made from fine powdermade according to the process of Example 6. This fine powder contained0.098 mol % (0.41 wt %) EVE.

The resin from Example 6 was mixed with Isopar® K (Exxon Mobil Corp.,Fairfax, Va.) at a concentration of 0.207 g/g of resin and formed into apellet approximately 10 cm in diameter at a pressure of about 2070 kPa.The pellet was heated to about 50° C. and paste extruded into a tapehaving dimensions of about 0.076 cm thick and about 15.25 cm widethrough a die having a reduction ratio of about 100 to 1, at an averageextrusion pressure of about 15,000 kPa. The reduction ratio is the ratioof the cross sectional area of the extruder barrel to the crosssectional area of the extrusion die exit. The resultant tape wascalendared at a rate of 8.2 meters/minute at about 45° C. to about 0.015cm thick. The lubricant was removed by heating at 180° C. to 210° C. Thewidth of the dried tape was about 15.8 cm.

The resultant tape was stretched in the longitudinal direction at about250° C. and 15.24 meters/minute to a ratio of 2:1. The resultant tapewas about 13.5 cm wide. The resultant tape was stretched transversely at300° C. at 100% per second at a ratio of 6:1 in the transversedirection.

The membrane was first wetted with isopropyl alcohol and then immersedin a 28 wt % aqueous ammonium hydroxide solution at about 5° C. forthree hours. The reacted membrane was rinsed with DI water and air driedat room temperature. The reacted membrane became semi transparent inwater indicating it was hydrophilic. The unreacted membrane was white inwater, indicating it was hydrophobic.

EXAMPLE 17

An expanded functional copolymer comprising the copolymer of TFE and EVEwas reacted as follows.

Expanded functional TFE copolymer was made according to Example 6. Thisfine powder contained 0.098 mol % (0.41 wt %) EVE. The fine powder wasprocessed to a membrane according to the processes of Example 16.

The membrane was first wetted with isopropyl alcohol. The pre-wettedexpanded TFE copolymer membrane was immersed in 50 wt % aqueous sulfuricacid and held at 60° C. for 24 hours. The membrane was then rinsed withDI water and dried at 60° C. for 2 hours. FTIR spectra showed thepresence of the carboxylic acid (about 3300 cm⁻¹) functionality, showingat least some of the ester functional group was hydrolyzed to thecarboxylic acid.

EXAMPLE 18

An imbibed composite was prepared as follows.

An expanded functional TFE copolymer membrane made according to theprocess as described in Example 9 was made from a functional TFEcopolymer fine powder containing 1.8 mol % (7.7 wt %) PSVE madeaccording to Example 5. The expanded material had a mass per area of 5.2g/m². A solution of TFE-PSVE ionomer, having approximately 18 mol %PSVE, was prepared according to the teachings of Wu et. al. [US2008/007036] in Paragraphs 113-114 and then diluted with ethanol and DIwater to 13.2%wt % solids in a 13.2% water/73.8% wt % ethanol solution.This ion exchange material solution was coated on a FLUOROJU™ film(Mitsubishi Plastics, Inc) placed onto a glass plate. The coating wasdone using a draw down blade with a coating gap of 7 mil (178 microns).The composite membrane was then stretched over the wet coating andallowed to infiltrate. After infiltration, it was dried for 20-60seconds with a hair drier. Then, a second coating of the same ionexchange material solution was done using a 1.5 mil (38 microns) gap.The second coating was then also dried with a hair drier for 20-60seconds. This imbibed composite membrane on the FLUOROJU™ film on theglass plate was placed in an air furnace at 160° C. for 3 minutes andthen removed to cool. The imbibed composite membrane was then removedfrom the FLUOROJU™ film backer. The final measured thickness of thisimbibed composite membrane was 12±2 microns. This material wassubsequently tested as a solid polymer electrolyte in a fuel cell byfirst forming a Membrane Electrode Assembly (MEA) using standardprocesses such as those described in US 2007/007206, paragraph 121. ThisMEA was subsequently tested using standard fuel cell test protocols suchas those described in US 2007/007206. A polarization curve wassuccessfully obtained indicating the imbibed composite membrane wasacting as a solid polymer electrolyte.

EXAMPLE 19

An inventive solid polymer electrolyte membrane was prepared using theprocess described in Example 18 using a starting expanded membrane witha mass per unit area of 5.2 g/m², except that in this example theinitial coating draw down gap was 5 mil (125 microns) and the seconddraw down gap was 3 mil (75 microns). The final measured thickness ofthis imbibed composite membrane was 12±2 microns. The measured Gurley ofthis sample was greater than 200 seconds. Further testing showed theGurley was greater than 1000 seconds, and greater than 5000 seconds, andgreater than 10,000 seconds.

EXAMPLE 20

The procedures of Example 18 were repeated except that the startingexpanded material made according to Example 9 was made from a functionalresin containing 1.4 mol % (6.1 wt %) PSVE made according to Example 5.This membrane had a mass per area of 1.6 g/m². The initial coating drawdown gap was 6 mil (150 microns) and the second draw down gap was 3 mil(75 microns). The final measured thickness of this imbibed compositemembrane was 12±2 microns. The imbibed composite material produced inthis example also successfully performed as a solid polymer electrolyteas indicated by the polarization curve obtained from the MEA preparedfrom the material.

EXAMPLE 21

The procedures of Example 18 were repeated except that the —SOOF pendantgroups in the starting expanded material containing 1.7 mol % (7.7 wt %)PSVE were converted to the acid form, —SO₃H. The starting membrane wasfirst wetted with IPA and then immersed in a 20 wt % KOH solution(Aldrich) at 100° C. for 72 hours. It was then rinsed with DI water andwas immersed in 15 wt % nitric acid (Aldrich) at 80° C. for 24 hours.The converted membrane was further boiled in DI water at 15 psig for 60hours and then air dried at room temperature. The starting membrane hada mass per area of 5.2 g/m², The imbibed composite membrane had athickness of 12±2 microns. The imbibed composite material produced inthis example also successfully performed as a solid polymer electrolyteas indicated by the polarization curve obtained from the MEA preparedfrom the material.

EXAMPLE 22

The procedures of Example 21 were repeated except that the startingexpanded material containing 1.4 mo % (6.1 wt %) PSVE had a mass perarea of 1.6 g/m². The —SOOF pendent groups in the membrane wereconverted to the acid form, —SO₃H. The membrane was converted and thenboiled in DI water according to Example 21. The final measured thicknessof this imbibed composite membrane was 12±2 microns. The imbibedcomposite material produced in this example also successfully acted as asolid polymer electrolyte as indicated by the polarization curveobtained from the MEA prepared from the material.

EXAMPLE 23

Three beads were prepared by paste extrusion of three different polymersas described below:

Polymer A) A fine powder resin comprising the copolymer of TFE and PSVEhaving 1.1 mol % PSVE. The break strength of the beading was 28.5 N.

Polymer B) A fine powder resin comprising a copolymer of TFE and PSVEhaving 1.0 mol % PSVE was comprised of a blend of 30% by weightcopolymer of TFE and PSVE having a 3.6 mol % of PSVE, and 70% by weightmodified TFE made in accordance with the teachings of U.S. Pat. No.6,541,589.

Polymer C) A fine powder resin comprising a copolymer of TFE and PSVEhaving 1.1 mol % PSVE was comprised of a blend of 80% by weightcopolymer of TFE and PSVE having a 0.7 mol % of PSVE, and 20% by weightcopolymer of TFE and PSVE having a 2.7 mol % of PSVE.

A 113.4 g sample of each polymer resin was blended together with Isopar®K at a ratio of approximately 0.250 g/g of resin. The blend wasconditioned at 49° C. for 10-12 hours. A 2.54 cm diameter cylindricalpreform was made by applying about 1,860 kPa of preforming pressure forabout 20 seconds. The extruder barrel was 2.54 cm in diameter and theram rate of movement was approximately 1.5 cm/min. The Isopar® K wasremoved from the beading by drying the beading in a restrained manner at49° C. for about 24 hours.

The break Strength of the beading was measured using an Instron® tensiletester using an initial sample length of 2.54 cm and a crosshead speedof 2.54 cm/min. Results for matrix tensile strength reported in Table 8are the average of 3 or more tests.

TABLE 8 Beading Matrix Tensile Strength Matrix Tensile Strength (kPa)Polymer A 7,612 Polymer B 7,302 Polymer C 6,343

Approximately the first and last 2.5 m of the extruded beading werediscarded to eliminate end effects. A 1.9 cm section of the extrudedbeading was expanded at a ration of approximately 35:1, by stretching at250° C. to at a constant true strain rate of 1 s⁻¹ (the engineering rateat the start of expansion is 100%/s). Approximately a 30 cm length fromnear the center of the expanded beading was removed, and the maximumbreak load of the removed sample held at room temperature (23° C. plusor minus 1.5° C.) is measured using an Instron® tensile tester using aninitial sample length of 2.54 cm and a crosshead speed of 2.54 cm/min.The matrix tensile strength was calculated from the maximum break loadand the mass of the sample tested.

TABLE 9 Expanded Beading Matrix Tensile Strength Matrix Tensile Strength(kPa) Polymer A 171,096 Polymer B 194,156 Polymer C 126,607

The expanded beading was then wet with IPA and submersed in 20% byweight % KOH in water at 175° C. for 4 hours. The expanded beading wasthen removed, rinsed with de-ionized water and submersed in 15% byweight nitric acid in water at a temperature of 175° C. for 4 hours. Theexpanded beading was then removed, rinsed and air dried.

The samples were then submersed in water and only the expanded beadingmade with the blend of two functional TFE copolymers, Polymer C, washydrophilic as it became translucent.

1-50. (canceled)
 51. A medical device comprising an expanded polymericmaterial comprising a functional TFE copolymer material having amicrostructure characterized by nodes interconnected by fibrils whereinthe TFE copolymer comprises a polymer chain of TFE and at least onecomonomer having a functional group that is pendant to the polymerchain.
 52. The medical device of claim 51 wherein the expanded polymericmaterial further comprises at least one bioactive species immobilizedthereto.
 53. The medical device of claim 52 further comprising a spacerarm.
 54. A medical device comprising an expanded functional TFEcopolymer material characterized by nodes interconnected by fibrilscomprising a copolymer of TFE and at least one comonomer having an aminefunctional group that is pendant to the polymer chain, and apolysaccharide immobilized thereto. 55-67. (canceled)